xjdropper

So the other day I cooked the top end of my 4.0. I had been thinking for a long time that I wanted to do a diesel swap. My MOS in the guard was Diesel mechanics, and I have done several fry oil (WVO) conversions to vehicles that already had a diesel engine. The problem with most swaps is Diesel engines are almost all heavy as hell. The Cummings 4BT is commonly swapped in but the thing is over 700 lbs. that is big block teritory. The mercedes 240d or 300d look promising but aren't the cheapest choices. Then I found a little 3 cylinder ford cm274 mower/tractor. Hmmm well this raises the question - just how much horsepower do you NEED? I am not trying to set any speed records, I don't need to go over 65 and most of my driving is 35 mph, so would 27 tiny horses hold a jeep at 65? I am sure with a small turbo I could get 30 maybe even 35 horses but if I can get away with just 27 I would be ok with that.

OttawaXJ

700hp minimum for a buggy on 54" tires and tube frame with 14bolt front and rear. Front obviously has a D60 outer.

sthon

How is that helpful?

sthon

OP No way in hell 27HP will get you to 65. Maybe with a tail wind or a 10% grade downhill...

Nick-B

Some of the small Japanese pickups from the 80's & 90's had small, 4 cyl diesel engines as an option. The problem is finding one in running condition, but I'm thinking one of those would meet your needs. Making it fit the Jeep drive train might be a bigger problem.

BKohs

From 85-87 there was a turbo diesel option in the XJ. They used a Renault J8S motor and it only had like 80-85HP. I would think with only 27-35HP you would be pushing the limits of what the motor could do.

DieselD

Lol. If that lil tractor engine could get yout to 65 I bet it would be going through hell keeping you there. Probably wouldn't last long. If you can find one, a 1.6L VW diesel could work. Someone on here was putting a slightly smaller Cummins in an XJ.

If you could deal with the electronics a newer VW 1.9 TDI would get some crazy MPGs.

BKohs

A good engine management system and someone who could tune it would make that 1.9 a great engine for the XJ. Plenty of power and great MPG's. I've had one of them up to over 50mpg doing about 70 on the highway.

DieselD

I know. That's pretty much my pipe dream, an XJ with a 1.9 VW TDI, 5spd 4x4 a 30 gallon tank, I could potentially go 1300 miles on a tank!

There's a company I seen while googling that made a kit to put a 1.9 in a YJ and possibly an XJ they made or used some sort of aftermarket ECM. I think if you sourced the 1.9 fom a manual trans VW then you could use the whole stock ECM but I'm not sure.

While I'm thinking, the XJs get their tach signal from the CPS right? And the speedo from the tcase's speedo sensor, so if you left it all in place, couldn't the guages function without the 4.0 being there?

holycaveman

I have a 1.6. With oversize tires it wouldn't reach 65. My opinion.

The 1.9 though would be great!

xjmarc

It's all in the gearing. How do you think 60hp Yotas turn 40" tires.

kirknd4spd

I'm gonna say you'll need at least 100 hp. My 2.5 has roughly 120 hp iirc, and it will exceed the speed limit on pretty much any road, until you get to a hill, then you're struggling to maintain 55. And overdrive is pretty much useless unless you're going at least 65-70, and forget about pulling up a hill in overdrive.

If I were doing a diesel swap, it would be a 4BT Cummins with an NV4500 behind it. Realistically, that's all I'd even consider.
Although the 850 series Perkins diesel would probably work great in a Jeep as well, around 115 hp and weighs 595 lbs. But I'm not sure how much more difficult of a swap that would be, and it would probably be more expensive too.

OttawaXJ

He didnt give specs. just said whats the minimum... well 25hp is the minimum if you're running on 4 donut tires off a toyota Corolla

I'd say the 190hp you have from the factory is the minimum for doing highway driving on 33s.

So really the point was quite obviously. If you ask a question without giving detailed parameters we're just going to make up our own and thus not answer your question

sthon

holycaveman

Very slooooooowwwwww.

Gearing is great, but speed takes HP. Especially with over sized tires.

Something like 18hp loss loss for every 100 lbs of rotating mass. Not literal of course. But to reach the same efficiency.

My friend wheels a 4 banger yota on 37 pit bulls. Crazy gearing. He just watches me on the hills. He can not even attempt them.